1. Field of the Invention
The present invention relates to a working device which is equipped with a tool rest suitable for working a noncircular workpiece, such as a piston of an internal combustion engine.
2. Description of the Related Art
FIG. 7 shows a piston for an internal combustion engine. The piston 10 has a main body 12 formed from an aluminum casting, and the main body 12 has a through hole 13 into which a piston pin pierces. Although a head 15 of the piston main body 12 is also formed from an aluminum casting, a groove portion 14 which receives a piston ring is made of cast iron. That is, the piston 10 is formed from dissimilar metal materials of aluminum casting and cast iron.
In the lathe turning of an outside diameter portion of this piston 10, the piston which is a workpiece is held by a work spindle and rotated and the outside diameter portion is machined by use of a cutting tool T1.
Because the piston 10 has a noncircular (oval) outside diameter profile, noncircular cutting is performed by moving the tool T1 back and forth in synchronization with the rotation of the workpiece 1.
In performing this noncircular working, it is possible to perform noncircular working by reciprocating a usual tool rest in synchronization with the rotation of the work spindle.
However, a tool rest is equipped with a large number of working tools and has a large weight and, therefore, the tool rest has also a large inertial force. Therefore, the tool rest cannot cope with high-speed reciprocal movements.
The Japanese Patent Laid-Open Publication No. 5-200601 discloses a working device for noncircular working provided with a tool rest dedicated to noncircular working.
In the noncircular workpiece shown in FIG. 7, which is formed from dissimilar metals, it is necessary to perform groove working for a ring in addition to the cutting of an outside diameter portion.
Therefore, it is preferred that a noncircular working device be equipped with multiple tools suited to different materials and the different working of the materials.
The object of the present invention is to provide a noncircular working device equipped with multiple tools suited to different materials and the different working of the materials.